|Subject: Re: [harryproa] Re: Changes|
|From: "Rob Denney" <email@example.com>|
|Date: 3/17/2008, 9:47 AM|
On Mon, Mar 17, 2008 at 9:03 PM, Mark Stephens <mark@harryproa.
> Rob has requested I not make any further 'negative' comments on this
> group. I believe that a discussion group should be open and free to
> express an opinion without it being seen as disparaging; a discussion
> group that only allows the views of the moderator is of little value.
> As Harryproa is now Rob's I will honour his request and
> not make any further posts. I do reserve the right of reply to Rob's
> last post and hope it is seen as a useful discussion.
My request was in a personal email in totally different context to
that above. I don't discuss personal emails on public forums so that
is all I will be saying about it.
If Mark (or Fritz, or Todd or any of the other dissenters i have
welcomed to the group in the past) want to post, they are welcome.
The only posts that have ever been censored on this group (2943-2946)
were from me and were chopped without my permission a week before I
Replies to the rest when I cool off a little.
> > G'day,
> > On Wed, Mar 12, 2008 at 10:14 PM, Mark Stephens wrote:
> > > I've never been quite sure about the extra sailing loads argument
> as the rigging loads on a cat are taken by strips of uni in the top
> and bottom of the bulkheads, not a big deal.
> > There is about as much material in these strips as in the glass which
> > goes around the hull to support the harryproa mast.
> I agree.
> > comparisons are:
> > 1) The cat has a substantial transverse bulkhead to keep the strips
> > apart and take the sheer loads, and a substantial compression post
> > under the mast, all of which needs to be very solidly glassed to the
> > very solid bridgedeck, hull and cabin roof. Some also have fore and
> > aft bulkheads to prevent the main beam buckling.
> > Harryproas have a single ring frame in the hull. Weighs less than 10
> > kgs glassed in.
> True but a catamarans bulkheads don't just hold the rig up they also
> hold the hulls together, segregate the boat into cabins, holds up the
> bridgedeck etc etc. Either only include the extra uni reinforcing in a
> cats bulkhead or add the weight of a proas beams to make weight
> comparison fair. The mast compression post isn't very heavy, usually
> just a piece of western red cedar glassed to the bulkhead.
> > 2) The fore and aft loads on the cat are enormous and require the
> > hulls to be beefed up (either with extra material or bigger
> > dimensions), plus a forebeam, a seagull striker and a mainsheet
> > traveller with a large beam to support it.
> No extra material is needed for fore/aft loads, the existing
> dimensions and laminates are enough to take care of these. True about
> the forebeam and mainsheet track but these are no heavier than the
> heavy balestron boom. Not having so many mainsheet control winches on
> a proa is a big plus.
> The forebeam then needs a
> > lot more hull height to keep it out of the waves. Not only heavy and
> > added windage, but it is in the extreme bow of the boat adding to the
> > pitching moment.
> Agree with this. Not having a fore beam and tramp is a great safety
> advantage and Harryproas certainly pitch a lot less than cats.
> > Harryproas have a simple stringer along the deck and the keel between
> > the beams. Maybe another 10 kgs.
> Modern cats don't have any stringers along the deck but do have souls
> and webs to walk on. Proas require an extra layer of glass over the
> leeward hull between the beams to take the mast loads, about 50kg.
> > 3) Cats, especially those with the user unfriendly 3 stay rigs also
> > need considerable structure to support the chainplates. Minimum is a
> > decent thickness half bulkhead, solidly glassed to the hull and deck.
> Most catamarans use an existing bulkhead to attach chainplates with
> some extra reinforcing.
> > Harryproas don't.
> > 4) The cat needs beefing up of the cabin top to take the headsail
> > track loads and the winches for the sheets.
> Not really much beefing up. A well designed saloontop with enough
> glass and thickness to support walking on will be enough to take the
> jibsheet loads with maybe an extra layer around the jib sheet track.
> Again, not having winches is a big proa benefit.
> > Harryproas don't.
> > > Also weight isn't necessarily a big factor. Where a proa saves
> weight is in not having so much material as they don't have such an
> extensive fitout, and not so much solid bridgedeck and saloon. I think
> a proa built with the same accommodation and appointment as a cat will
> weigh about the same.
> > Weight is a huge factor. Blind Date has 2 doubles and a single berth
> > with space for 2 more single cabins , huge deck space, covered
> > cockpit, galley, large nav station and toilet. It weighs 2 and a bit
> > tonnes/tons in sailing trim. There are no catamarans with similar
> > usable space that are anywhere near this weight. Lower weight means
> > smaller motors, smaller rigs, higher speeds, lower build and
> > maintenance costs, less to paint, easier to haul out, etc etc.
> Blind Date is a very nice boat and very light but it is also very
> basic with no saloon and very little deck space, being mainly tramp,
> one outboard, no anchor winch etc. It would be more appropriate to
> compare Rare Bird which weighs 3.7 tonnes empty because it has of a
> fitout more similar to a cat, though still only one hull fitted out.
> My original comment was to say a proa with the same level of fitout
> doesn't have a huge weight benefit. Put the same fitout of the typical
> cruising cat on a proa and it would be a dog and may not even shunt.
> Proas need to be kept light so they can take advantage of their
> waterline length of the leeward hull and not bog down their fat
> windward hull. Keep them light and they are magic.
> > The owner and I are working on tenders to build a 60' charter proa
> > optimised to take advantage of the proa and unstayed rig benefits.
> > The shell, bulkheads and beam materials are a touch under 2 tonnes
> > based on surface areas and laminates. This boat has 4 double cabins
> > (2 with island beds) each with a toilet and shower, a huge saloon and
> > covered deck space, plus enough cabin top to mount enough solar panels
> > to power the electric motors. Ready to charter it will weigh and
> > cost less than most 40' cats and outperform most 60 foot cats
> > according to the same spread sheet that accurately predicted Blind
> > Date's weight,.
> That will be very impressive if it can be achieved.
> > >Where a proa gets it's performance is in the extra waterline length.
> > It's pretty pointless comparing proas with cats as they are such
> > different beasts fulfilling different rolls.
> > The harryproa role is cruising comfortably and safely for a given
> > price . Most cat owners would say the same. Harryproas do this
> > extremely well. Look at http://www.youtube.
> > Has anyone sailed on a cruising cat at 15 knots boatspeed in 15 knots
> > wind speed in such comfort with such low stress? Mark Giles, who has
> > test sailed a lot of cats (and one harryproa) for Multihull World
> > magazine hasn't. The cat fulfills this role comparatively poorly,
> > unless the comparison is with a mono.
> Rare Bird is a joy to sail as are all the Harryproas I have sailed on.
> Nobody is disputing that.
> > Waterline length is part, but not all of the story. Other important
> > factors are:
> > The reduced drag from not having daggerboards and their slots.
> > Reduced weight and windage of superstructure that isn't compromised
> > for rigging loads and daggerbboards.
> > All the weight concentrated in the middle of the boat.
> > Higher righting moment for a given weight.
> > More efficient hull beam to length ratios.
> > Better rigs.
> > Superior hull forms (no rocker, high prismatic) which are not
> > compromised for tacking.
> As I said, cats and proas are very different beasts. Harryproas have a
> lot of great advantages which is why I like them so much, if I had the
> money I would buy Rare Bird tomorrow.
> Speaking of which the estate is desperate to sell Rare Bird. Anyone
> interested in making an offer approaching $200,000 would land them
> selves an absolute bargain and own a very special boat.
> All the best and goodbye,